Demystifying the Date of Easter & Pascha

A Method for Calculating Easter, 1456 AD

This year, churches in the West observed Easter 35 days before the Eastern Orthodox Church celebrated Easter (usually referred to as Pascha).  The date of Easter/Pascha has generated a great deal of confusion over the years.  To help clear the fog, I have attempted a non-technical explanation of how these dates are calculated and why they vary so much.

Ecclesiastical vs. Astronomical Dates

According to the Council of Nicaea (325 AD), Easter/Pascha is celebrated on the Sunday which follows the first full moon after the Vernal Equinox.*  Setting the date of this holy day would seem to be simple and straightforward.  Nevertheless, the Eastern and Western churches don't base their calculations on actual astronomical events, which were difficult to calculate with precision in the fourth century.  As an article on the website, Time and Date, points out:  

►March 21 is the church's date of the vernal equinox, regardless of the time zone, while the actual date of the equinox varies between March 19 and March 22, and the date depends on the time zone.

►The date of the Paschal Full Moon, used to determine the date of Easter/Pascha, is based on mathematical approximations of the monthly lunar cycle, which follows a longer 19-year cycle called the Metonic cycle.

Approximating the Vernal Equinox

The ecclesiastical dates for the vernal equinox and the first full moon may coincide with the dates of their associated astronomical events, but in some years they don't.  For example, based on astronomical dates alone, Easter/Pascha would fall on March 24 in 2019.  But based on the ecclesiastical dates it was celebrated on April 21 by the Western churches and April 28 by the Orthodox Church.  

Calendar Wars

Adding to the confusion, the Eastern and Western churches use different calendars to mark the date of the vernal equinox, which both churches designate as March 21.  

►On our modern, Gregorian calendar, used by the Western churches, this date falls within 2 days of the astronomical event.  

►But on the more ancient Julian calendar, March 21 occurs 12-15 days after the astronomical event.  The Julian calendar, owing to its lack of precision, is currently 13 days behind the Gregorian calendar.  So March 21 on the Julian calendar occurs on April 3.  The earliest possible date for Pascha in the Orthodox Church is thus April 4.  

►The continued use of the Julian calendar by the Orthodox Church is a source of constant friction between groups within the church, and largely accounts for the frequent discrepancy between the dates of Western and Eastern Easter/Pascha.

The Paschal Full Moon 

The calculation of the Paschal Full Moon also hinges on the calendar, since the full moon and the date of Easter/Pascha must be after the Vernal Equinox.  In the West, the Paschal Full Moon is within 1-2 days of the astronomical full moon.  But under the Julian calendar, the Paschal Full Moon is 3-5 days after the astronomical event.  

►This creates a complex interplay between the calendars, such that the difference between the Western and Eastern celebrations may vary from 0 days to 35 days!

►According to the Time and Date website (see graph, below), the dates coincide about 30% of the time.  They are only 1 week apart 44% of the time.  On the other end of the spectrum, they are four or five weeks off 26% of the time.  This large discrepancy happens when the Gregorian Paschal Moon occurs before March 21 (the vernal equinox) on the Julian calendar, "causing the Orthodox date to jump ahead to the next Full Moon."

Who's Right?

The Nicene Council linked the date of Easter/Pascha to astronomical events rather than to a particular date on a calendar.  Hampered by the mathematical and observational limitations of ancient astronomy, the church adopted a convenient and practical method for approximating the date.  This method ensured that Easter/Pascha was celebrated by churches on the same day (though this was not always the case in the beginning due to different calculation methods).  

Given the advances in astronomy since that time, this workaround is no longer necessary.  Exact calculations based on the movement of celestial bodies can now be projected many decades into the future.  

If the Eastern and Western churches are not ready to make this adjustment, the next best solution is the universal adoption of the Gregorian calendar.  This calendar aligns much more closely with actual astronomical events than the Julian calendar.  As that calendar continues to drift from the actual vernal equinox and full moon, the date of Orthodox Pascha will occur later in the year.   

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* Appendix: The Date of Passover.  According to the Eastern Orthodox Church, the Council's method for calculating the date of Pascha also entailed that the Resurrection cannot be celebrated before the Jewish Passover, since the crucifixion took place in conjunction with the Passover.  On the other hand, it was also clear that the Council's intent was to completely separate the church from the lunar calendar used by the Jews. Thus in Western churches the date of Easter sometimes occurs before Passover.  But this is never the case in the Eastern Church.  As a result, there will still be occasional discrepancies in the date of Easter/Pascha even if the calendars are properly aligned and both churches continue their practice of approximating the date of the vernal equinox and the Paschal Full Moon.  See the Orthodox Wiki discussion on the Zonaras Proviso.  I avoided this issue in the article because it would have added another complex layer to the presentation.  

Special thanks to Mike Luc for his suggestions on improving this piece.

Sources:

https://www.timeanddate.com/calendar/determining-easter-date.html 

https://www.timeanddate.com/news/calendar/two-easter-dates-why-so-late 

https://orthodoxwiki.org/Paschalion 

https://www.goarch.org/-/fordham-pascha  

Chemtrails, Contrails, & Geoengineering

These three concepts are often conflated by the public, which has led to a raft of conspiracy theories.  Many chemtrail advocates maintain that the persistent condensation trails (CONTRAILS) which appear behind commercial jets are a form of geoengineering intended to cool the climate.  The overspreading trails are said to be composed of chemicals, concocted by the government, whose composition may be harmful to humans and the environment.  

Though the facts tell a much different story, there are good reasons to be concerned about the unpredictable and potentially dangerous effects of large-scale climate engineering.  Those concerns are shared by many scientists, environmentalists, and politicians.  You don’t have to wear a tin foil hat to conclude that reengineering the atmosphere could have disastrous consequences.

Now the science.  Geoengineering proposals to seed the atmosphere with particles that reflect sunlight in order to cool the earth, have little in common with aircraft CONTRAILS.  The particles, usually Sulfur dioxide, have to be dispersed in the stratosphere at an altitude of 20 km or higher (the higher the better).  This is about twice the height of commercial aircraft flights and well beyond the service ceiling of such aircraft.  Dispersing the particles below 19 km - 20 km (i.e., in the troposphere) would be far less effective, resulting in a much shorter residence time for particles due to turbulence, mixing, and descending air currents which would carry them to earth.  

With a heavy payload of chemicals, there are very few, if any, high-altitude aircraft that can loft that much weight to such heights.  Consequently, the task would require specially modified vehicles, custom designed vehicles, or other technologies such as rockets and balloons (above).  A number of journal articles have been written evaluating different aerial platforms for performing “stratospheric aerosol injection” (SAI).  The preferred solution appears to be an entirely new aircraft, the Stratospheric Aerosol Injection Lofter (SAIL).  To date, this aircraft is only a concept (right).  

So what about aircraft CONTRAILS?  They form when the water vapor, generated by combustion inside the jet engine, turns to ice crystals (water vapor is a natural by-product of burning fossil fuels).  Their persistence is a function of temperature and humidity, which can be forecasted with a reasonable degree of accuracy from daily, upper air observations.  

But more to the point, CONTRAILS have exactly the opposite effect sought by geoengineering:  They tend to warm the climate instead of cooling it, even though they block a slight amount of sunlight (left).  The thin ice crystal clouds (cirrus) allow most shortwave solar radiation to strike the earth. This warms the surface.  Heat from the surface radiates skyward in the form of longwave radiation, which is reflected back (reradiated) by the CONTRAILS.  The net effect is a slight increase in atmospheric temperature.  Consequently, scientists have sought to limit CONTRAIL effects by proposing different technologies, fuels, and flight paths that would mitigate their formation.

The upshot is that there is no connection between persistent aircraft CONTRAILS (so-called “chemtrails”) and attempts to cool the atmosphere through geoengineering.  If some climate activists had their way, contrails would disappear tomorrow.  In the meantime, large scale attempts to inject particles into the stratosphere should be prohibited, and the science behind those efforts should be met with deep skepticism.  Our knowledge of the atmosphere is still rudimentary in many ways.  If we damage it, there is no backup system.

Right:  An infrared satellite image showing dozens of contrails over the southeastern United States during a single morning in January 2004. Yale Environment 360.   NASA

Sources:

Effects of Different Stratospheric SO2 Injection Altitudes on Stratospheric Chemistry and Dynamics

Stratospheric aerosol injection tactics and costs in the first 15 years of deployment

Review of possible very high-altitude platforms for stratospheric aerosol injection

Optimizing Injection Locations Relaxes Altitude-Lifetime Trade-Off for Stratospheric Aerosol Injection

How Airplane Contrails Are Helping Make the Planet Warmer

We Could Refreeze Earth’s Melting Poles With Aerosol-Spraying Planes

Solar Geoengineering: Should we artificially cool the planet?

Education's "Big Lie"

In 1978, the ACLU defended the right of Neo-Nazis to hold a peaceful rally in Chicago, complete with Nazi uniforms and swastikas. The right of the Nazis to assemble without impediment was upheld under the First Amendment by the US Supreme Court.

 
It should be evident that the ACLU was no friend of the Nazis. They abhorred everything the Nazis stood for.  In fact, the lawyer who argued the case was Jewish!  Nevertheless, the ACLU chose to act on principle, because First Amendment protections do not discriminate based on the content of one’s speech (with a few notable exceptions).  If the rights of Nazis to speak can be denied, then so could the rights of any group that is despised or happens to fall out of favor with society.

It is possible, then, to treat others with whom we disagree or even dislike, with respect and tolerance. This is the essence of civil discourse and it is one of the principles that makes America great.

 
Fast forward to our present situation. Much of our education system has exchanged this principle of free speech for what can only be called, the ‘Big Lie.’  In the battle over sexuality and gender, children are being taught that they must accept and endorse lifestyles that they may find morally objectionable. It is not enough to tolerate LGBTQ values, children are encouraged to become “allies” and display symbols of LGBTQ pride, etc.

 
Even principled criticism of LGBTQ beliefs, regardless of how respectful it is expressed, is liable to hurt the feelings of LGBTQ children. This is construed as a form of hate and bullying. Progressive educators have thus devised a perfect ploy for forcing the desired political behavior from students, namely LGBTQ advocacy.

This Big Lie has undermined the noble principle exhibited by the ACLU in their defense of the Nazis, namely, that tolerance and respect do not entail agreement, much less advocacy.  Like all people, LGBTQ students are entitled to respect. However, their chosen lifestyle and values are not automatically entitled to approval or admiration. But, alas, this distinction is too nuanced for activist educators who only see the world in black and white.  

See: https://en.wikipedia.org/wiki/National_Socialist_Party_of_America_v._Village_of_Skokie  https://www.pbs.org/video/wttw-specials-skokie-invaded-not-conquered/